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96 lines
3.0 KiB
Racket
96 lines
3.0 KiB
Racket
6 years ago
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#lang br/quicklang
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(require "grammar.rkt" brag/support racket/pretty racket/stxparam)
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(provide (except-out (all-from-out br/quicklang) for if print) (all-defined-out) pretty-print)
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(module+ reader
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(provide read-syntax))
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(define-lex-abbrev reserved-terms
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(:or "=" "def" "(" ")" ":" ","
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"return" "for" "in"
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"+" "-" "*" "/" "<" ">" "\""
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"if" "else" "print"))
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(define-lex-abbrev indent (:: (:+ "\n") (:* " ")))
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(define prev-indent 0)
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(define pending-dedents 0)
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(define (lex ip)
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(define inner-lex
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(lexer
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[(eof) (cond
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[(> prev-indent 0)
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(set! pending-dedents prev-indent)
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(set! prev-indent 0)
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(lex input-port)]
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[else eof])]
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[(from/stop-before "#" "\n") (token 'COMMENT #:skip? #t)]
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[indent
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(match-let* ([(list _ spaces) (regexp-match #rx"^\n+( *)$" lexeme)]
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[this-indent (/ (string-length spaces) 2)])
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(define tok
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(cond
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[(> (- this-indent prev-indent) 1) (error 'only-one-indent-please)]
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[(> this-indent prev-indent) (token 'INDENT)]
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[(< this-indent prev-indent)
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(set! pending-dedents (- prev-indent this-indent))
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(lex input-port)]
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[(= this-indent prev-indent) (token lexeme #:skip? #t)]))
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(set! prev-indent this-indent)
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tok)]
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[(:+ whitespace) (token lexeme #:skip? #t)]
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[reserved-terms (token lexeme (string->symbol lexeme))]
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[(:+ (:- (:or alphabetic punctuation) reserved-terms))
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(token 'ID (string->symbol lexeme))]
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[(:+ (char-set "0123456789"))
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(token 'INTEGER (string->number lexeme))]))
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(cond
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[(equal? (peek-char ip) #\") (token 'STRING (read ip))]
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[(> pending-dedents 0)
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(set! pending-dedents (sub1 pending-dedents))
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(token 'DEDENT)]
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[else (inner-lex ip)]))
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(define-macro top #'begin)
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(define-macro (assignment ID EXPR)
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#'(define ID EXPR))
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(define-macro-cases comparison
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[(_ ARG) #'ARG]
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[(_ LARG OP RARG) #'(OP LARG RARG)])
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(define-macro sum #'comparison)
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(define-macro product #'comparison)
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(define-macro (func-def ID ID-ARGS STMT ...)
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#'(define (ID . ID-ARGS)
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(let/cc return-cc
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(syntax-parameterize ([return (make-rename-transformer #'return-cc)])
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STMT ... (void)))))
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(define-syntax-parameter return (λ (stx) (error 'not-parameterized)))
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(define-macro func-app #'#%app)
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(provide (rename-out [my-for for]))
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(define-macro (my-for ID EXPR . STMTS)
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#'(for ([ID (in-list EXPR)])
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. STMTS))
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(define-macro block #'begin)
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(provide (rename-out [my-if if]))
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(define-macro-cases my-if
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[(_ COND TBLOCK) #'(when COND TRUE-BLOCK)]
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[(_ COND TBLOCK FBLOCK) #'(if COND (let () TBLOCK) (let () FBLOCK))])
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(provide (rename-out [my-print print]))
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(define-macro (my-print EXPR)
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#'(display EXPR))
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(define (read-syntax src ip)
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(define parse-tree (parse (λ () (lex ip))))
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(strip-context
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(with-syntax ([PT parse-tree])
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#'(module _ pythonesque-demo
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#;(pretty-print 'PT)
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PT))))
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